Over the last couple of decades a large variety of communication devices have become available for common use. Some of these devices include the personal computer (PC), personal digital assistant (PDA) and cellular (or “wireless”) telephone. The ushering in of these new devices and the coming into prominence of the Internet during the 1990s has resulted in an increased number of independent communication networks. Unfortunately, exclusivity of networks is often undesirable, especially from a consumer standpoint, since it does not allow communication across device platforms.
To address the problems associated with multiple devices on multiple networks, solutions have been sought that unify device service across multiple platforms. One emerging protocol, which is used to establish “sessions” over an Internet Protocol (IP) network, is the Session Initiation Protocol (SIP). SIP is a request-response type protocol that resembles two other Internet protocols, HTTP (Hypertext Transport Protocol, which is the underlying protocol used by the World Wide Web) and SMTP (Simple Mail Transfer Protocol, which is a protocol used to send e-mails between servers). While the development of SIP is progress in the right direction, more innovations are needed.